Toromys rhipidurus ( Thomas, 1928 )

Emmons, Louise H. & Fabre, Pierre-henri, 2018, A Review of the Pattonomys / Toromys Clade (Rodentia: Echimyidae), with Descriptions of a New Toromys Species and a New Genus, American Museum Novitates 2018 (3894), pp. 1-52 : 38-39

Toromys rhipidurus ( Thomas, 1928)

Echimys rhipidurus Thomas, 1928: 291 (original description).

TYPE SPECIMEN AND TYPE LOCALITY: The holotype (by original designation, BMNH 28.7.21.89), an adult male skin and skull collected by R. W. Hendee on 25 January 1928 at “ Pebas. Up. Amazons, 300′,” Loreto, Peru .

DIAGNOSIS AND DESCRIPTION: Much smaller than Toromys grandis ( tables 5, 6), dorsum finely grizzled yellow-brown agouti heavily lined with black, sides paler yellowish; rostrum in front of and below the eyes, inner rear of thighs, dorsal and ventral tail base, and sometimes a lateral line are dull rust red-orange or red tinged ( figs. 13B , 14C , 16 ). Small, pale yellow postauricular patches are prominent in life, but not evident on most specimen skins ( fig. 14C , 16 ). Aristiforms narrow, black or banded with ochraceous-buff subterminal bands, tipped dusky or ochraceous yellow ( fig. 4E ). Underparts pale gray-brown, sometimes with a white band between the elbows or white chest patches ( fig. 16 ); gray color imparted by white-based and pale-tipped hairs with wide subterminal gray bands. Tail distal to the dorsal extension of body hair onto the base with long, monocolor black or dark rust-brown hairs above, which can nearly cover the scales proximally, but which shorten and thin distally to expose the scales at the tail tip, such that the tail appears conical; tail hairs paler laterally; self rusty at base below. Scales at dorsal tail base longer anterior-posteriorly than wide laterally, with strongly curved posterior edges (like fish scales, fig. 5C ). Feet brown to grayish above; with sparse ungual tufts shorter than the strong claws. Plantar surfaces black pigmented, as for genus described above. Eyes mahogany brown, with pointed-ovoid, vertically slit pupils. Cranium robust, rostrum short and broad, and nasals slightly pinched in medially ( fig. 9B ). Jugal fossa deep and pointed anteriorly, with a strong ventral lip. Postglenoid fossa with or without a strong beaded lip of petrosal bone below. The space between the auditory meatus and ridge of squamosal above it as wide as or nearly the width of the meatus. Squamosal usually extends as a triangular tongue into the top of the mastoid process ( fig. 7B ). Medial parietal-interparietal suture between the temporal ridges generally strongly recurved anteriorly or with a medial notch (12/17), but can be straight (5/17, including the holotype). Upper molars with narrow lophs at right angles to the cranial axis, lophs notably parallel and of even width, and traversed by narrow parallel flexi in a distinctly laminar occlusal pattern ( fig. 12D ). First two lower molars with straight, angled posterolophids ( fig. 12D ). Incisor faces deep to medium orange; the upper incisor roots arise posterior to the anterior base of the maxillary zygoma.

NATURAL HISTORY. Little has been recorded of the habits of this species, other than that it is generally arboreal and can use tree hollows. A number of localities where specimens were collected are in white sand, “ varillal ” habitat (Río Nanay), a specialized ecosystem that harbors endemic plants and vertebrates (e.g., Alonso and Whitney, 2001).

SPECIMENS EXAMINED: PERU: Loreto, Pebas ( BMNH 28.7 .21.89 [holotype]); Río Napo, Lago Mirario (not located), ( BMNH 32.8 .4.21, 32.8.4.22); Boca Río Mazán , ( BMNH 32.8.4.22a); Maynas, Puerto Indiana; ( AMNH 73231 , 73266–73277 *, 73791); Orosa , Amazon River , ( AMNH 74084–74086 *) ; Genaro Herrera (= Jenaro Herrera ), ( AMNH 276710 ) ; Iquitos, Pampa Chica , ( FMNH 87243 , 87244 *, 87245–87248) ; Río Nanay, Santa Rita , ( FMNH 87249 ) ; Río Manití, Santa Cecilia ( FMNH 87249–87252 ) ; Maynas, Quistococha , ( FMNH 122991 , 122992 ) ; Nazareth, Río Yavary , ( FMNH 19854 ) .

Figures

FIG. 13. Head colors of specimens. A, Toromys, sp. nov. LSUMZ 8904; B, Toromys rhipidurus FMNH 87248; C, Makalata cf. macrura LSUMZ 14408. Specimens in panels A and C were collected at Yarinacocha (type locality of Toromys, sp. nov.). The tip of the muzzle is variably buff to rusty in Toromys sp. nov. (fig. 16), while Makalata from some distant populations are not as bright rusty as A. On Makalata, the rust color extends well behind the eye above and below. Also note the coarser, more robust vibrissae of both Toromys, the more developed fringe of salient wispy hair on rim of the Makalata ear (also typical of Pattonomys spp.), and the less robust claws of T.sp. nov. compared to those of T. rhipidurus.

FIG. 14. Living Toromys and Pattonomys. A, Toromys grandis, lower Rio Purus, (fig. 1, locality 31). Note the elongate body, the longer black hair on the proximal tail, and the broad foot with narrow heel. There is a postauricular patch of pale skin. The anterior bright eyeshine spot seems to show an oval, vertical pupil, the other spot is a reflection of the flash (image by Vinicius Carvalho). B, Pattonomys semivillosus in a black mangrove tree (Avicennia germinans) in Parque Nacional Isla de Salamanca, Magdalena, Colombia. The white postauricular tufts above and behind the ear are striking (photograph by Fabrice Schmitt). C, Toromys rhipidurus, captured near Iquitos, Peru. The evident cream-colored postauricular patches are not visible on most museum skins. The camera-flash has accentuated the yellow midbody hues (image by Pamela Sánchez-Vendizú).

FIG. 16. Toromys skins, dorsal and ventral. T. rhipidurus FMNH 87248 (right), tail cropped during photography and rotated somewhat during preparation; T. albiventris FMNH 55483 (holotype; left), this skin is shrunken, the head and body lengths on the skin labels of the two taxa are approximately the same (table 5). Scale bar = 5 cm.

FIG. 4. Pelage of dorsum at rump. A, Leiuromys occasius. FMNH 84529, high density of sharply pointed spines and fine, wavy red underhairs; B, Pattonomys semivillosus USNM 280204, dense, more tapered, white-tipped spines, abundant pale bristles, straight ochraceous underhairs; C, Makalata cf. didelphoides USNM 549593, agouti pelage, sparser narrowly buff-tipped spines, tapered hairlike spine tips; D, Toromys grandis AMNH 94036, thick bristles, no spines; E, T. rhipidurus AMNH 73273, fine-banded agouti bristles; F, T. sp. nov., narrow aristiforms and a few narrow spines with hairlike tips, abundant thin, agouti bristles. The resemblance between Toromys congeners is evident. Spine tips are more sharply tapered in A than in B.

FIG. 5. Scales and hairs on dorsal tail base. A, Pattonomys carrikeri USNM 496483, irregular scales nearly square or slightly hexagonal, hairs unicolored, long, and curled outward; B, Leiuromys occasius FMNH 84259, short, wide hexagonal scales in spiral rows, short, adpressed, scalelike hairs in pairs; C, Toromys rhipidurus AMNH 276710, scales rounded posteriorly, about as long as wide, hairs robust, unicolor, black or rusty; D, Makalata macrura USNM 496480, short, rectangular scales in even rows, fine, salient hairs that are often banded dark at base, pale at tips. White scale bars 5 mm, fluid-fixed specimens except B.

FIG. 9. Crania, dorsal view. A, Toromys grandis AMNH 93601; B, T. rhipidurus BMNH 28.7.21.89 (holotype); C, T. sp. nov., FMNH 55483 (holotype), D, Leiuromys occasius. AMNH 71897; E, Pattonomys punctatus BMNH 98.12.1.18 (holotype); F, P. flavidus USNM 63218 (holotype); G, P. carrikeri AMNH 130790; H, P. semivillosus USNM 280205. Black arrow in A indicates recurved parietal-interparietal suture, white arrow the expanded squamosal shelf.

FIG. 7. Crania and mandibles, lateral view. A, Toromys grandis AMNH 93601; B, T. rhipidurus BMNH 28.7.21.89 (holotype); C, T. sp. nov., FMNH 55483 (holotype), D, Leiuromys occasius. AMNH 71897; E, Pattonomys punctatus BMNH 98.12.1.18 (holotype); F, P. flavidus USNM 63218 (holotype); G, P. carrikeri AMNH 130790; H, P. semivillosus USNM 280205. Black arrow in F indicates the deep mandible of P. flavidus relative to its congeners.

FIG. 12. Occlusal patterns of upper (top row) and lower (bottom row) toothrows of Toromys and Pattonomys species, not to scale. A, Toromys sp. nov. FMNH 55483 holotype; B, T.sp. nov. LSUMZ 8904, an old individual; C, Toromys grandis AMNH 93604; D, Toromys rhipidurus AMNH 98667; E, Pattonomys carrikeri AMNH 31530; F, P. semivillosus USNM 280205; G, P. punctatus BMNH 9812118 (holotype). In Toromys maxillary teeth (A–D) note laminar appearance of narrow, nearly parallel molar flexi, lophs of nearly uniform width, and mures lingually (left) of center of teeth. In Pattonomys (E–G) note short, offset flexi, short, wide protoloph (arrow) especially pronounced on M2, mures about in midtooth; unequal loph sizes give irregular appearance. On mandibular teeth, note the straight (flat) posterior molar edges; the square (flat) lingual edge of central lophid (entoconid) in Toromys (A–D, also compare with fig. 17).